Public awareness of climate change went global two years ago with the emergence of the Fridays for Future movement. For good reason, people are trying to improve the earth’s atmosphere by cutting emissions. Human activities over the past 50 years have driven greenhouse gases to a higher level than at any time in the last 800,000 years. The environmental footprint in the field of medicine is also big – five to ten percent of emissions in Western countries are attributable to the healthcare sector. Many areas are already being addressed. The “Green Hospital” concept is a growing trend that has hospitals monitoring waste and energy use to help establish a sustainable healthcare system. Operating rooms can play their part in reducing the carbon footprint. The spotlight is on anaesthetic gases, because about a third of a hospital’s greenhouse gas emissions are generated by the use of anaesthetic gases. 

Standard forms of anaesthesia are characterized by their low fresh gas flow into the machine’s breathing gas system. In the past, the fresh gas flow was generally used in very high concentrations in order to ensure that the anesthetic was as safe as possible. This is the straightforward approach for anaesthetists. By using high flow, they can control the anesthetic and therefore don’t have to manage the anesthesia as much. It is a bit like driving an SUV: safe and comfortable, but not really environmentally friendly. 

The carbon dioxide equivalent of the inhaled anesthetic amounted to around three million tons in 2014. This provides an indication of how much a certain amount of a particular greenhouse gas contributes to global warming compared to the same quantity of carbon dioxide. The volatile anesthetics are halogenated hydrocarbons – highly potent greenhouse gases, some of which stand out with particularly high global warming potential (GWP). In the Kyoto Protocol adopted in 1997, it was agreed that there should be a global reduction in the amount of halogenated hydrocarbons; in Kigali in 2016, it was resolved that they should be phased out completely by 2035. However, anaesthetics were exempted because they are medically necessary substances. The problem is that there has been a sharp global increase in the use of volatile anesthetics. This is due to improved medical care and an aging patient population that is operated on more frequently.

Minimal- and low-flow anesthesia can cut anesthetic gas emissions by up to 90 percent – while also benefiting the patient and the environment. During low-flow anesthesia the fresh gas flow is reduced to a maximum of 1 l/min, while a maximum of 0.5 l/min is used during minimal-flow anesthesia.

By way of example, a seven-hour anesthesia with a fresh gas flow of 0.5 l/ min and two percent inhaled anesthetic causes a greenhouse effect roughly comparable to that of a 500-mile car trip. With a conservative fresh gas flow (which uses around 4–8 l/min) this could soon add up to 9,320 miles, depending on the anaesthetic agent. As a preventive measure, a basic requirement for anesthesia with low fresh gas flow is a rebreathing system with absorber, which removes and binds the exhaled carbon dioxide from the breathing cycle. Moreover, unused gases and anesthetic agents from the patient’s exhaled air are also reused. As a general rule, the lower the fresh gas flow, the higher the rebreathing component and thus the smaller the agent consumption and the negative impact on the environment.

“Flow as low as you can go!” says Professor Manuel Wenk, explaining the motto that has guided his work ever since his residency days. After being appointed chief consultant of the Department of Anesthesiology, Intensive Care Medicine, and Pain Management at the Florence Nightingale Hospital run by the Kaiserswerther Diakonie in Düsseldorf, he switched to using volatile anesthetic agents in the hospital’s operating rooms. Until then, total intravenous anaesthesia (TIVA) was almost exclusively used in Germany. Wanting to protect the environment, Wenk committed himself to reducing the waste associated with the disposable products needed for TIVA. “Everybody was surprised at how quickly the impact became evident,” says the doctor. In order to ensure that he wasn’t jumping out of the frying pan into the fire, he opted for lowflow anaesthesia from the very beginning. “Our younger colleagues in particular are pressing for things to be done differently,” says Wenk, confirming the commitment to change. Since the hospital linked its anesthesia workstations and added the Dräger Connect data analytics application, successes in gas agent reduction can now be evaluated – as a team, of course: “We are not competing with one another. It is more about working in a way that is as efficient and environmentally friendly as possible – and Dräger Connect helps here."

While low- and minimal-flow anaesthesia offer compelling benefits, the approach has not yet been widely adopted around the world. Dr. Jeffrey Feldman, Professor of Clinical Anesthesiology at the Children’s Hospital of Philadelphia, located in Philadelphia, USA, is an advocate for low- and minimal-flow anaesthesia. In a children’s hospital, persuading colleagues to reduce flows can be especially challenging as sevoflurane is the most commonly used inhaled anesthetic. It is well known that sevoflurane produces Compound A when used with certain types of carbon dioxide absorbents. Although Compound A can be nephrotoxic in rats, this risk has never been verified in humans. Furthermore, modern carbon dioxide-absorbent formulations do not produce Compound A. Nevertheless, the guidelines from the United States FDA state that flows of less than 1 liter per minute should never be used with sevoflurane and many practitioners do not use less than 2 liters per minute. 

“I naturally try to convince my colleagues of the safety and benefits of lowflow anesthesia,” says the doctor, who is committed to protecting the environment and has published professional articles documenting the safety of low-flow anesthesia. “Since anaesthetists adjust the fresh gas flow, each of them is responsible for the environmental impact of the anaesthetic vapors and gases,” he says – and wishes to appeal to his colleagues’ sense of responsibility. “Even though the environmental impact of one single case may be small, it is still a good idea to reflect on habits that extend across an entire career.” His appeal is also aimed at the manufacturers of volatile anesthetics. “It is time to drop any concerns about low flow rates and ask both the manufacturers and the regulatory authorities to remove all restrictions from their requirements,” he says. “We owe it to society to work on minimizing our carbon footprint.”

In a recent study, the use of low-flow anaesthesia in a US hospital equipped with 600 beds led to a 64 percent reduction in carbon dioxide, which equates to 2.8 million kg. This is equivalent to the annual emissions generated by more than 600 cars. In addition, using low-flow anesthesia cut the cost of volatile anesthetics by $ 25,000 – per month. Some hospitals have made considerable progress in reducing their inhaled anesthetic foot[1]print, while others are still at the beginning of the process. It is essential to measure the current level of emissions and track the progress made. Prof. Manuel Wenk and his team are looking forward to the first annual evaluation of their 12 anesthesia workstations with the help of Dräger Connect. One colleague is currently in the process of reviewing the switchover from intravenous to volatile anesthesia management – taking into account all parameters. The fact that the team has stopped using disposable coffee cups in the operating area and also rides bicycles around the city cannot be taken into account here – although it is good for their personal carbon footprint.